1. Field of the Invention
The present invention relates to a device for the transmission of electrical power signals of variable frequency and phase from a stationary assembly to a rotary assembly.
2. Summary of the Prior Art
For the transmission of electrical power from a stationary part to a rotating part it is already known, for example from FR-A-2 521 766, to use a rotary transformer having fixed first armature part which carries a primary winding, and a rotary second armature part which faces the first part and carries a secondary winding. This known arrangement is suitable for the transmission of a periodic electric power signal at a fixed frequency (generally an industrial frequency ranging from 50 to 400 Hz) and of known shape (particularly sinusoidal).
However, this arrangement is not suitable when it is desired to obtain on the rotating part an electrical signal of which the shape, the frequency and the phase must be variable to a wide extent and, for optimum output, it is necessary to operate the entire installation at resonance. The voltage/current phase shift may be achieved in the primary circuit by means of a capacitor in a well known manner, but the insertion of a second capacitor into the secondary circuit is difficult to envisage for technical reasons associated with its volume and the rotational speed of the rotary assembly. The consequence is that it is impossible to obtain constant power at the terminals of the secondary circuit if the supply frequency varies between 0 and 10,000 Hz. Moreover, it is impossible to transmit different signals without correspondingly increasing the number of transformers.